Fix uptime (#207)

* fix uptime

src/rpi-cpu2mqtt.py

@@ -209,9 +209,11 @@ def check_sys_clock_speed():
 def check_uptime(format):
     if format == 'timestamp':
         full_cmd = "uptime -s"
+        tz_cmd = "date +%z"
+        tz_str = subprocess.Popen(tz_cmd, shell=True, stdout=subprocess.PIPE).communicate()[0].decode('utf-8').strip()
         timestamp_str = subprocess.Popen(full_cmd, shell=True, stdout=subprocess.PIPE).communicate()[0].decode('utf-8').strip()
         timestamp = datetime.strptime(timestamp_str, '%Y-%m-%d %H:%M:%S')
-        iso_timestamp = timestamp.isoformat() + 'Z'  # Append 'Z' to indicate UTC time
+        iso_timestamp = timestamp.isoformat() + tz_str  # Append correct offset to indicate `local` time
         return iso_timestamp
     else:
         full_cmd = "awk '{print int($1"+format+")}' /proc/uptime"